B6. Pressure from invasive species

a. Freshwater invasive species

b. Marine (coastal) invasive species

c. Terrestrial invasive species

Type: Pressure Indicator

Indicator Description

Non-native species are those that have reached Great Britain by
accidental human transport, deliberate human introduction, or which
arrived by natural dispersal from a non-native population in
Europe. Species that have arrived since 1500 are included
within this indicator. Most non-native species are considered
benign or positive but some have a negative impact on native
species through the spread of disease, competition for resources,
or by direct consumption, parasitism or hybridisation; such species
are termed invasive. Invasive non-native species have one or
more of these negative impacts and a high capacity to spread to
natural and semi-natural habitats. The indicator shows the
change in number of invasive non-native species established across
10% or more of the land area of Great Britain, or along 10% or more
of the extent of its coastline.

Summary

There are 3,163 non-native species in Great Britain, 1,980 of
which are classified as established (reproducing in the wild).

This indicator contains 190 non-native species that are
considered to be exerting a negative impact on native biodiversity
(46 freshwater species, 36 marine species and 108 terrestrial
species). The majority (184) of these species are established;
six1 are long-term resident but
not known to breed in the wild.

Over the period 1960 to 2017, invasive non-native species have
become more prevalent in the countryside. Since 1960, the number of
these species established in or along 10% or more of Great
Britain’s land area or coastline has increased in the freshwater,
terrestrial and marine (coastal) environments, thereby increasing
the likely pressure on native biodiversity.

Comparing the latest period (2010 to 2017) with the previous one
(2000 to 2009), the number of invasive non-native species
established in or along 10% or more of Great Britain’s land area or
coastline has remained constant in terrestrial environments (at 56
species), and has increased in both freshwater (from 12 to 13
species) and marine environments (from 23 to 28 species).

Figure B6i. Number of non-native invasive species
established in or along more than 10% of Great Britain’s land area
or coastline, 1960 to 2017.

Notes: The last time period covers a shorter
period than the other bars (from 2010 to 2017).

1The six long-term residents species
included the indicator are two species of terrapin (Emys
orbicularis, Trachemys scripta) and four freshwater
fish (Ameiurus melas, Leuciscus idus,
Salvelinus fontinalis, Oncorhynchus
gorbuschas).